Thursday, 17 March 2011

My most recent experience of goose-bumps (aka goose-flesh) was watching the latest episode of Being Human, the BBC's supernatural drama. This rather odd form of emotional reaction, in which a chill is felt and bumps form on the skin and the hairs stand erect, was noted by Darwin and has continued to intrigue scientists. Unfortunately, past research into 'piloerection' (to use its technical name) has been hampered by the lack of an objective measure.

Previous experiments relied on participants indicating when they were experiencing the feeling. This is problematic: the feeling might be illusory; participants' internally-focused vigilance creates an unnatural situation; and the act of indicating how one is feeling can interfere with other physiological measures taken at the same time. Now Mathias Benedek and Christian Kaernbach have taken a fresh look at goose-bumps using a new objective measure - a camera that records the skin of the forearm and uses an algorithm to detect the trade-mark pimpling and raising of the hairs.

Benedek and Kaernbach wired fifty undergrads (seven males) up to their new piece of kit. The students then listened to four music clips and four clips from films (each between 90 seconds and five minutes long). These were from a larger selection picked for their power to provoke goose-bumps. Examples included My Heart Will Go On, performed by Celine Dion; Only Time, performed by Enya; a scene from Armageddon (in which the astronaut says good-bye to his daughter before sacrificing his own life for the good of mankind); and a scene from Braveheart (featuring a stirring speech by William Wallace).

The study threw up a host of new findings. The film clips were a more reliable provoker of goose-bumps than the music clips (24 per cent vs. 11 per cent). The participants had heard of most of the music and film material, but there was a tendency for unfamiliar clips to have more goose-bump power. Overall it was fairly tricky to provoke goose-bumps, with only 40 per cent of the clips doing so. There was also a gender difference - none of the men experienced goose-bumps vs. 47 per cent of the women - but this has to be taken with caution because there were so few men in the sample.

Sometimes there was a mismatch between the objective measure of goose-bumps and participants' self-report. On 34 per cent of the occasions that their hairs stood on end, participants didn't report they had goose-bumps. Contrarily, on 11 per cent of trials, participants said they had goose-bumps when in fact they didn't. These data highlight the risks associated with relying on self-report.

From a theoretical perspective the most important findings relate to the physiological correlates of goose-bumps. One existing theory states that goose-bumps are a marker of peak arousal. The current study found that goose-bumps correlated with increased heart rate and blood pressure. On the other hand, breathing deepened during goose-bumps, and participants reported feeling more 'moved' when they had goose-bumps, not more aroused, neither of which is consistent with the peak arousal account.

Another hypothesis holds that goose-bumps are provoked by sadness, creating a cold sensation which promotes an evolutionary advantageous desire for social reunion. Benedek and Kaernbach said the increased heart rate, deep breathing (non-crying sadness has these effects too) and feeling of 'being moved' are consistent with this account. However, they also acknowledged that previous studies have found that goose-bumps are often pleasurable. Taken altogether, the researchers think goose-bumps probably reflect a distinct emotional state, a kind of awed mixture of fear and joy. In English and French we lack a dedicated word for this, but in German they have 'Rührung' and 'Ergriffenheit', which means something similar.

The researchers' conclusion is that given the low specificity of other physiological measures of emotion, measuring goose-bumps objectively could prove to be a useful new tool in the psychologist's armamentarium when studying emotional responses.
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